Ricky is on a long road trip. He wants to drive 390390 miles in the next 88 hours. Some of the time he will be able to drive 6060 miles per hour, and some of the time he will have to drive slower at 3030 miles per hour. If Ricky accomplishes his goal and drives exactly 400400 miles in 88hours, how many hours does he drive at 6060 miles per hour?

the answer is 5

but I thought it is 400-240 not 390-240

because it says he drove 400 miles